The best advice I can give would be to learn electronics from almost anywhere except audio forums.
If you're swapping out electrolytic capacitors from a power supply or audio amplifier, you won't go far wrong if you pick one of the reputable Japanese brands: Panasonic, Nichicon, Rubycon, Nippon Chemi-Con or Sanyo.
Choose a family with as long a rated lifetime as you reasonably can, and with a temperature rating of 105 deg C - even if the amp never runs anything like that hot, a cap rated for higher temperatures will last considerably longer.
If you can, look up the spec of the original parts and choose a replacement with a similar ESR. If you can't find the original spec, then a "low ESR" replacement is likely to be OK, but avoid ultra-low ESR parts unless you know the circuit is designed for them (possibility of stability problems).